Improvement in lifting-jacks



H. T. MORRISON.-

Improvement in Lifting-Jacks. NO. 115,086, vPatented May23,8?l.

gtturuey,

UNITED STATES PATENT OFFICE.

HACKLEY T. MORRISON, OF LAWRENOEVILLE, VIRGINIA.

IMPROVEMENT IN LlFTlNG-JACKS.

Specification forming part of Letters Patent No. 115,086, dated May 23, 1871.

spring pin and pointer.

This invention has for its object to enable a screw-jack to work continuously either while lifting or lowering, and while the lever by which the screws are rotated is turning back as well as while it is turning forward, to the end that there may be no lost motion 5 which object is accomplished by the provision of two separate screws, arranged one above the other, one of which raises or lowers itself in the footpiece, while the other raises or lowers the headpiece, said screws working alternately.

Referring to the drawing, a is an ordinary foot-piece for a lifting-jack. b is a nut, placed centrally of and flush with the top of the same. c is the central orifice within the foot-piece. d is the screw that passes through the nut b down into the orifice c. c is a cylindrical block placed above the foot-piece and pierced centra-l] y at its lower end by the screw d, to which the block is rigidly fastened so as to turn with it. f is a circular ratchet rigidly secured to and outside of the block e'at the lower end of the same. g is a lever pivoted upon the block c just above the ratchet f. h is a pawl pivoted loosely at one end to the under side of the lever g, and, when 'turned forward, engaging at its free end with the ratchet f. k 7c are springs, secured at their rear ends to a block, fi, that is attached to the lower side of the lever g, and at their front ends bearing, one at a time, upon the pawl h, according as the same is turned to one side or the other of its pivot, and keeping the pawl engaged with the ratchet f. A pin, l, passing horizontally through the foot-piece a enters at its inner end one of the longitudinal grooves m, of which there are several in the exterior of the screw d. A spring, n, inclosed in a tube, j,

and encircling the pin l, presses the saine inward. The inner end of the pin l is beveled at one side, while the other side is straight.

The object of this construction is to enable lthe straight side ofthe pin to operate as a stop by catching in one of the grooves m and thus preventing the screw from rotating backward, while the beveled side enables the screw, when rotated forward, to press the pin outward, so that the latter then presents no obstacle to turning the screw. rlhe pin l may be turned so as to act as a stop to prevent the backward rotation of the screw either while the same is moving upward or downward. A

of the lever g, pawl h, and ratchet f, the pin l holding the screw stationary while the pawl travels back to get a fresh hold. To make the screw move downward the pawl h must be turned entirely around sok as to engage with the ratchet at a point on the other side of its pivot from that at which it engages when the screw is moving upward, vand the arrow o should be made to point downward. By this arrangement the screw d remains stationary half the time, and the block e rises or descends, as the case may be, also only halt' the time, the moving of said block being effected solely by the rotation of the screw d. The other half of the time is occupied by the rest of the apparatus, not yet described, in

continuing` the lifting or lowering operation of thc jack so as to make it incessant.

Upon the iiange p of the block c rests a cylindrical block, e', having a central chamber for the reception of the block e. The block e serves as the foundation for an apparatus in all respects the duplicate of that above described, and indicated in the drawing by the same letter, with the addition of the mark 'that indicates corresponding parts in the lower mechanism. The duplicate levers g and g are connected by a block, q, in the outer end or which a recess, o', is made for the reception of the bar by which the levers are worked. The upper mechanism operates alternately with the lower one, the two pawls, h and h', being placed at different angles, so that while the 1.. rlhe screw d, provided with longitudinal v grooves m, end combined with the spring-pin Z having a beveled end, as specified.

2. The arrangement of the spring-pin l with the pointer o, as described. Y

3. The arrangement of the head and foot pieces a a, screws d d', blocks e e', ratehets f j", ps1-Wis h h', levers g g', and spring-pins l l',

as explained.

HAGKLEY T. MORRISON.

'Vtnesses:

Taos. A. GREENE, E. R. TURNBULL. 

